CGAL users discussion list

[Peter Hachenberger <>]

Hi Andy,

with 3D Nef polyhedra it is not a problem to do intersection of planes
and polyhedra. The problem in your case is the file format. We don't
support stl files at the moment. I can write a constructor for stl files
for you in an hour, but it will not be very efficient. It will construct
every facet as a separate Nef polyhedron, compute the arrangement of the
facets, and transform the final arrangement into a solid by defining all
enclosed regions as the interior. I have such a constructor for off
files and it should not be hard to adapt it. So now the question is, how
big your input data is, and how important the construction efficiency is
for you. If you have solids of a few thousand facets, then I the
constructor will converts your solids into a nef3 file in around an
hour. I once converted the famouse bunny (34835 vertices, 69473 facets)
into a nef3 file. That took a bit longer than one hour.

Peter

On Fri, 2008-04-11 at 12:45 +0200, Andy Hirsh wrote:
> Dear listener
> 
> I would like to know if it's possible (of course, using CGAL!) to
> evaluate the intersection between a plane and a concave polihedron...
> the goal is to cut some steleolithographic objects defined with the
> .stl file format
> (http://local.wasp.uwa.edu.au/~pbourke/dataformats/stl/).
> 
>   thanks a lot
> 
>         Andy